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  • 1.
    Ahmed, Sheikh Ali
    et al.
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Blom, Åsa
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University.
    Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally-modified European aspen and downy birch wood2017Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 63, nr 1, s. 74-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study is to investigate if these properties enhanced in thermally-modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC, showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth. Whereas, a significant anti-mold effect was observed on Beckers oil treated samples.

  • 2.
    Ahmed, Sheikh Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy2013Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, nr 1, s. 57-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

  • 3. Ahmed, Sheikh Ali
    et al.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, nr 2, s. 251-258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in uneven distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 4.
    Ahmed, Sheikh Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Development of a new rapid method for mould testing in a climate chamber: Preliminary tests2013Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, nr 4, s. 451-461Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12-14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.

  • 5.
    Ahmed, Sheikh Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood: Impact of drying, thermal modification, and copper-based preservative2013Inngår i: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 85, s. 284-288Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of mould on wood surfaces depends on several factors. Although mould does not affect the mechanical properties of wood, it greatly reduces the aesthetic value of wood like the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are also a great concern. Different types of dried and treated wood were used to observe whether they had enhanced durability against mould following an accelerated laboratory test method in a climate chamber. Samples were green, air-dried, industrially thermally-modified, treated with copper-based preservative, and kiln-dried wood, which were tested within a single test run. The test produced the following main results: the thermal modification increased the durability of the wood, and the protective effectiveness of alternative treatments was comparable to that of commercially available copper-based treatment. However, the initial moisture content of the samples during mould exposure had a great influence on the onset of mould growth. The risk of mould susceptibility of industrial kiln-dried lumber can be reduced by drying using the double-layering technique which likely forced the nutrients to deposit near the evaporation surfaces followed by planing off the nutrient enriched edges.

  • 6.
    Ahmed, Sheikh Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Yang, Qian
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Accelerated mold test on dried pine sapwood boards: Impact of contact heat treatment2013Inngår i: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, nr 3, s. 174-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ‘‘sapwood out’’ and ‘‘sapwood in’’ positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). Accelerated mold test was performed in a climate chamber where naturally mold infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides which accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth was 170°C for 10 min. But, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.

  • 7.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT-studies during the Conditioning phase of the Wood Drying Process2018Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Computed tomography (CT) during drying of sawn timber is an excellent non-destructivetechnique to study the moisture flux as a function of drying time. In this study, a climatechamber combined with a medical CT- scanner has been used for non-destructive studies ofdensity changes in sawn timber during drying and conditioning.Green sawn timber contains large amounts of water and has to be dried before it can befurther processed and used in various building applications. The most common dryingmethod is convective air-circulation drying in large industrial kilns, where the relativehumidity (RH) of the hot circulating air is gradually reduced until the timber reaches thetarget moisture content (MC).Drying of sawn timber is driven by the existence of a difference in MC between the coreand the surface, so that moisture moves from the wet inner region towards the drier outerregion. During the early capillary stages of drying, the drying rate is high while, at the laterstages when all liquid water has evaporated, the drying rate is slow and diffusioncontrolled.At the end of the drying process, the timber surface is always drier than its core.In addition to this moisture gradient, internal stresses develop within the cross section withcompression stresses in the timber surface and tension in the inner regions. To avoidunwanted distortions, both these stresses and the moisture gradient, need to be eliminatedbefore the timber is further processed. This is achieved in a final conditioning stage withinthe drying process by moistening the circulating air through steaming or water spraying.The aim of the present work was to optimize the conditioning stage by developing amethod for studying of moisture gradients, deformations and internal and externaldimensional changes in sawn timber during the conditioning phase by using a CT-scannercombined with a drying unit for in-situ measurements of moisture flow.The results show that it is possible to detect the moisture gradient between the surface andcore of the timber with satisfactory reliability, but not the internal and external dimensionalchanges. However, this method creates a potential for increasing the knowledge andunderstanding of the conditioning phase and makes it possible to optimize and develop thisstep in the drying process to improve the yield and ensure a higher quality of the sawntimber.

  • 8.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The use of X-ray computed tomography in timber construction research2016Inngår i: New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA, Madison: Forest Products Society, 2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment means that processes such as drying, modification, water absorption, internal and external cracking and material deformation can be studied in temperature- and humidity-controlled environments. The data recorded by the CT during the process is converted into two- or three-dimensional images that for instance can show dynamic moisture behavior in wood drying.This paper gives an overview of the possibilities of using CT in timber construction research, and shows examples of applications and results which can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products for construction, and how to deal with different material combinations such as wood and metal.The practical application of the result is that CT-scanning, combined with image processing, can be used for non-destructive and non-contact 3-D studies of exterior constructions elements during water sorption and desorption, to study swelling and shrinking behaviour, delamination phenomena, crack development, etc.

  • 9.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Norwegian University of Science and Technology (NTNU), Department of ICT and Natural Sciences, Norway.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT scanning of capillary phenomena in bio-based materials2017Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, nr 4, s. 181-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive study of dynamic moisture processes in wood and other bio-based materials. In the CT facilities at Luleå University of Technology, it is possible to study wood-moisture relations such as water absorption, drying and related material deformation under a temperature- and humidity-controlled environment.An increase in the use of bio-based materials in building construction has led to an increased interest in capillary phenomena in these materials, because of an increasing number of moisture-related damage in timber and hybrid-timber buildings. This article shows some examples of how different bio-materials used in construction interact with liquid water over time. The overall purpose has been to develop the CT technique as a powerful tool for the determination and visualization of capillary flow that can be a base for modelling and an increased understanding of moisture flow in new bio-based building materials.Early-stage observation of the behaviour of different traditional and new bio-based building materials shows that CT scanning, combined with image processing, has a high potential to be used in performing non-destructive and non-contact tests that can help to increase the knowledge of water-material interactions and develop building materials with an optimized performance.

  • 10. Johansson, Dennis
    et al.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Effect of heat treatment on capillary water absorption of heat-treated pine, spruce and birch2006Inngår i: Wood structure and properties '06: [proceedings of the 5th IUFRO Symposium Wood Structure and Properties '06 held on September 3-6, 2006 in Sliač - Sielnica, Slovakia] / [ed] R. Lagana; S. Kurjatko; J. Kudela, Zvolen, Slovakia: Arbora Publishers , 2006, s. 251-255Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Longitudinal absorption of water in matched heat-treated and untreated boards was studied. The boards are from three different species. Scots pine (Pious sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens). The heat treatment was performed according to the Thermowood process at two different temperature levels (170 degrees C and 200 degrees C) for all three species. Computer tomography (CT) scanning was used to intermittently monitor the ascent of the water front. The use of CT scanning enables a study of the liquid water ascent in three dimensions over time. This means that it is possible to determine the influence of different treatment temperatures and species as well as the difference between heartwood and sapwood on capillary action.The results show that longitudinal water absorption in pine sapwood was substantially lamer when heat-treated at 170 degrees C compared to untreated pine sapwood. In pine heartwood, the ascent of water was low in heat-treated as well as in untreated boards. Spruce boards showed low water absorption in sap- and heartwood in heat-treated as well as in untreated boards. Birch showed a decreasing uptake of water with increasing treatment temperature

  • 11.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Myronycheva, Olena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Öhman, Micael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Multivariate modeling of mould growth in relation to extractives in dried Scots pine sapwood2017Inngår i: Proceedings IRG Annual Meetin, 2017, artikkel-id 17-20629Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Influence of extractives on mould growth on Scots pine sapwood dried in air or in kiln was studied. Boards were sprayed with water mixtures of spores of the fungal species Penicillium sp., Aspergillus sp., Mucor sp., Paecilomyces sp., Trichoderma sp., treated at a temperature of 22ºC at 90% RH, classified into a percentage of covered area. Acetone and water extracts were isolated and analyzed for sugars, nitrogen, ash, resin/fatty acids, glycerol, and phenols. A multivariate Orthogonal Partial Least Squares (OPLS) regression model was developed to study relations between the extent of mould coverage of boards and chemical content. The model describes 51% variability in X and 69% in Y with prediction power of 55%. The results indicated that total acetone soluble extractives and sugars like glucose contributed to increased mould growth whereas fatty acids prevent mould growth.

  • 12.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Yang, Qian
    Heat treatments of high temperature dried norway spruce boards: Saccharides and furfurals in sapwood surfaces2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 2, s. 2284-2299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbohydrates that migrate to wood surfaces in sapwood during drying might influence properties such as mould susceptibility and colour. Sugars on the surface of Norway spruce boards during various heat treatments were studied. Samples (350mm×125mm×25mm) were double-stacked, facing sapwood-side outwards, and dried at 110°C to a target moisture content (MC) of 40%. Dried sub-samples (80 mm × 125 mm × 25 mm) were stacked in a similar way and further heated at 110°C and at 130°C for 12, 24, and 36 hours, respectively. Glucose, fructose, and sucrose as well as 5-hydroxymethylfurfural (HMF) and furfural in the sapwood surface layer of treated wood were analysed using HPLC (RI- and UV-detectors). Carbohydrates degraded to a lower extent at 110°C than at 130°C. Furfural and to a larger extent HMF increased with treatment period and temperature. Heat treatment led to a decrease in lightness and hue of the sapwood surface of sub-samples, while chroma increased somewhat. Furthermore, considerably faster degradation (within a few minutes) of the carbohydrates on the surface of the dried spruce boards was observed when single sub-samples were conductively hot pressed at 200°C. Treatment period and initial MC influenced the presence of the carbohydrates in wood surface as well as colour change (ΔE ab) of the hot pressed sub-samples.

  • 13.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Larsson, Robert ()
    Virkestorkningens grunder: en bok för personer verksamma inom träindustrin samt för områdets utbildningar2007Bok (Annet (populærvitenskap, debatt, mm))
  • 14.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Analys av olika metoder för utformning av hörnskarv av tätningslist1983Rapport (Annet vitenskapelig)
  • 15.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Creep formation of the surface layer of timber boards during air circulation drying1992Inngår i: Understanding the wood drying process: a synthesis of theory and practice ; [proceedings of the] 3rd IUFRO conference on wood drying, August 18-21, 1992, Vienna, Austria, Wien: IUFRO , 1992Konferansepaper (Fagfellevurdert)
  • 16.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Cupping of center boards during drying due to anisotropic shrinkage1992Inngår i: Understanding the wood drying process: a synthesis of theory and practice : [proceedings of the] 3rd IUFRO conference on wood drying, August 18-21, 1992, Vienna, Austria, Wien: IUFRO , 1992Konferansepaper (Fagfellevurdert)
  • 17.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Desorptionsisoterm för furu och gran vid 20° och 50° C1984Rapport (Annet vitenskapelig)
  • 18.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Draghållfasthet och E-modul: nordsvensk furu och gran i området för artificiell torkning1984Rapport (Annet vitenskapelig)
  • 19.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Formförändringar hos virke: Torkning av granreglar från klentimmer2001Rapport (Annet vitenskapelig)
    Abstract [sv]

    Två delstudier har gjorts med syfte att studera träreglars formbeständighet vid industriell produktion av granreglar sågat från klentimmer. Delstudie I omfattar studier av virkesegenskapers, och då främst fibervinkelns inverkan på virkesdeformation men även processparametrar som virkeslängd, paketläggning samt belastning under torkning ingår. Delstudie II omfattar en liknande undersökning med processvariabler som ströavstånd och inverkan av konditioneringssteg på virkesdeformationer. Även högtemperaturtorkning i LTU:s labtork ingår för jämförelse.

  • 20.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Heat and Mass Transfer during Sapwood Drying above the FSP: Consequences for Kiln Drying2000Inngår i: 6th international IUFRO wood drying conference on wood drying research and technology for sustainable forestry beyond 2000., Marcel Dekker Incorporated , 2000Konferansepaper (Fagfellevurdert)
  • 21.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Högtemperaturtorkning av byggnadsvirke1990Rapport (Annet vitenskapelig)
  • 22.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Konditionering av furuvirke i samband med artificiell torkning1987Rapport (Annet vitenskapelig)
  • 23.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Vidaretorkning av furu: analys av torkningsskador1989Rapport (Annet vitenskapelig)
  • 24.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 10, Gran, modell 2, våttemperatur 50oC1984Rapport (Annet vitenskapelig)
  • 25.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 11, Gran, modell 3, våttemperatur 40oC1984Rapport (Annet vitenskapelig)
  • 26.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 12, Gran, modell 3, våttemperatur 45oC1984Rapport (Annet vitenskapelig)
  • 27.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 13, Gran, modell 3, våttemperatur 50oC1984Rapport (Annet vitenskapelig)
  • 28.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 2, Furu, modell 2, våttemperatur 40°C1984Rapport (Annet vitenskapelig)
  • 29.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 3, Furu, modell 2, våttemperatur 45°C1984Rapport (Annet vitenskapelig)
  • 30.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 4, Furu, modell 2, våttemperatur 50° C1984Rapport (Annet vitenskapelig)
  • 31.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 5, Furu, modell 3, våttemperatur 40°C1984Rapport (Annet vitenskapelig)
  • 32.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 6, Furu, modell 3, våttemperatur 45°C1984Rapport (Annet vitenskapelig)
  • 33.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 7, Furu, modell 3, våttemperatur 50oC1984Rapport (Annet vitenskapelig)
  • 34.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 8, Gran, modell 2, våttemperatur 40oC1984Rapport (Annet vitenskapelig)
  • 35.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: D. 9, Gran, modell 2, våttemperatur 45oC1984Rapport (Annet vitenskapelig)
  • 36.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Malmqvist, Lars
    Torkningsschema: Del 1 Teori, BASIC-program1984Rapport (Annet vitenskapelig)
  • 37.
    Morén, Tom
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Winberg, Pär
    Virkestorkningens grunder2004 (oppl. 2.)Bok (Annet (populærvitenskap, debatt, mm))
  • 38.
    Myronycheva, Olena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sidorova, Ekaterina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hyperspectral Imaging Surface Analysis for Dried and Thermally Modified Wood: An Exploratory Study2018Inngår i: Journal of Spectroscopy, ISSN 2314-4920, E-ISSN 2314-4939, artikkel-id 7423501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Naturally seasoned, kiln-dried, and thermally modified wood has been studied by hyperspectral near-infrared imaging between 980 and 2500 nm in order to obtain spatial chemical information. Evince software was used to explore, preprocess, and analyse spectral data from image pixels and link these data to chemical information via spectral wavelength assignment. A PCA model showed that regions with high absorbance were related to extractives with phenolic groups and aliphatic hydrocarbons. The sharp wavelength band at 2135 nm was found by multivariate analysis to be useful for multivariate calibration. This peak represents the largest variation that characterizes the knot area and can be related to areas in wood rich in hydrocarbons and phenol, and it can perhaps be used for future calibration of other wood surfaces. The discriminant analysis of thermally treated wood showed the strongest differentiation between the planed and rip-cut wood surfaces and a fairly clear discrimination between the two thermal processes. The wavelength band at 2100 nm showed the greatest difference and may correspond to stretching of C=O-O of polymeric acetyl groups, but this requires confirmation by chemical analysis.

  • 39.
    Myronycheva, Olena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Öhman, Micael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Distribution of low-molecular lipophilic extractives beneath the surface of air- and kiln-dried Scots pine sapwood boards2018Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, nr 10, artikkel-id e0204212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During industrial wood drying, extractives migrate towards the wood surfaces and make the material more susceptible to photo/biodegradation. The present work provides information about the distribution, quantity and nature of lipophilic substances beneath the surface in air- and kiln-dried Scots pine (Pinus sylvestris L.) sapwood boards. Samples were taken from knot-free sapwood surfaces and the composition of lipophilic extractives, phenols and low-molecular fatty/resin acids layers at different nominal depths below the surface was studied gravimetrically, by UV-spectrometry and by gas chromatography-mass spectrometry (GC-MS). The concentration of total extractives was significantly higher in kiln-dried than in air-dried samples and was higher close to the surface than in the layers beneath. The scatter in the values for the lipophilic extractives was high in both drying types, being highest for linoleic acid and slightly lower for palmitic, oleic and stearic acids. The amount of fatty acids was low in kiln-dried boards, probably due to a stronger degradation due to the high temperature employed. The most abundant resin acid was dehydroabietic acid followed by pimaric, isopimaric, and abietic acids in both drying types. It is concluded that during kiln-drying a migration front is created at a depth of 0.25 mm with a thickness of about 0.5 mm.

  • 40.
    Myronycheva, Olena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Öhman, Micael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Portable microNIR sensor for the evaluation of mould contamination on wooden surfaces2019Inngår i: Proceedings of the 62nd International Convention of ociety of Wood Science and Technology. Convention  Tenaya Lodge, Yosemite, California, USA, October 20-25: Theme: Renewable Materials and the Wood-based Bioeconomy, / [ed] LeVan-Green, S., SWST, Society of Wood Science and Technology , 2019, s. 46-51Konferansepaper (Fagfellevurdert)
  • 41.
    Myronycheva, Olena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Poohphajai, Faksawat
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. innoReNew, Slovenia.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Vikberg, Tommy
    RISE Research Institutes of Sweden, Skellefteå, Sweden.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Junge, Helmut
    ABiTEP GmbH, Berlin, Germany.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Application of GRAS Compounds for the Control of Mould Growth on Scots Pine Sapwood Surfaces: Multivariate Modelling of Mould Grade2019Inngår i: Forests, ISSN 1999-4907, E-ISSN 1999-4907, Vol. 10, nr 9, artikkel-id 714Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Research Highlights: In this study, the Generally Recognised as Safe (GRAS) compounds were applied in order to study mould-fungi growth on dried Scots pine sapwood. Background and Objectives: The transition to the use of more sustainable wood-material may be possible by applying GRAS compounds that can control and prevent contamination by primary colonising mould fungi. Materials and Methods: Kiln-dried sawn timber was treated with three different GRAS compounds, and different fungal inoculation methods applied in order to investigate differences in the development of fungal communities. Results: Substances based on potassium silicate significantly reduced fungal growth and mould contamination on the studied wood surfaces. By combining wood-surface treatments with GRAS compounds, fungal-area size as predictors and mould grade as response, a partial least squares (PLS) model that makes it possible to predict mould grade on wood surfaces was developed. The PLS model is a key component in the development of a smart grading-systems equipped by e.g. high-speed digital cameras for the early detection of fungal attack on wood surfaces in different applications. However, the measurements based on chemical characterisation should be the next step to take in order significantly to enhance the model and increase the range of robust applications. In the current study, a multivariate model describing the influence of each fungal-covering area on mould grade was presented for the first time.

  • 42.
    Myronycheva, Olena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Growth of mold and rot fungi on copper-impregnated Scots pine sapwood: Influence of planing depth and inoculation pattern.2018Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, nr 4, s. 8787-8801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The biocidal properties of an industrially used copper-based preservative were evaluated at different planing depths on exposure of pine wood to mold fungi in direct and indirect contamination methods, with simultaneous verification of white rot fungi virulence on wood. The preservative was an aqueous solution of copper carbonate, 2-aminoethanol, and quaternary ammonium compounds. Full cell preservative impregnation efficiency against visual mold fungi growth was tested on sapwood surfaces planed to different depths before impregnation. The virulence of two white rot fungal strains of Trametes versicolor (441 and JPEI) against the dried non-impregnated and impregnated wood samples was also tested. The unplaned surface of impregnated timber was occupied by air-borne contaminants, such as Paecilomyces variottiand Aspergillus niger up to 30%, and, even after impregnation it was necessary to process the surface to avoid micro-fungi settlement. The virulence of the tested rot fungi strains was confirmed by the aggressive degradation of non-impregnated wood with a mass loss of over 40%. Both Trametes sp. strains degraded the preservative-impregnated wood with a mass loss of 3.1% to 4.8%, but degradation by the JPEI strain was more intensive and more dependent on planing depth than the other strain (441).

  • 43.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Colour responses to heat-treatment of extractives and sap from pine and spruce2003Inngår i: Proceedings of the 8th IUFRO International Wood Drying Conference: Improvement and innovation in wood drying : a major issue for a renewable material : 24-29 August 2003, Brasov, Romania / [ed] Mihai Ispas; Sergiu T Chiriacescu, Brasov: Transilvania University of Brasov, Faculty of Wood Industry , 2003, s. 459-464Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Scandinavian sawmills have over the last 20 years adopted ever-higher temperatures in the dry kilns. The reason for this has been improvements in drying quality and kiln capacity. However, some problems relate to this strategy, mainly discolorations and extensive resin flow from knots and heartwood in pine. In this study, underlying factors for changing wood colour were investigated for spruce and pine. From the sapwood portions of wood, sap was extruded by mechanical compression, put in glass bottles and heat-treated at different temperature levels ranging from 60 °C to 95 °C during 1 to 5 days. Then the colour of the sap was measured using a standard colorimeter. Extractives from pine heartwood were also heat-treated and analysed in the same way. From these experiments it was concluded that much of the colour change in solid wood emanated from colour changes in constituents of the sap and extractives. Pine sap was more susceptible to colour change than sap from spruce. Also, an accelerated colour change was noticed above 70 °C for pine sap. Finally, it was observed that extracted wood that was soaked in water and then heat-treated still underwent some colour change, probably due to secondary hydrolysis of hemicelluloses.

  • 44.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Färgförändring vid värmebehandling av sav och extraktivämnen från furu och gran2002Rapport (Annet vitenskapelig)
    Abstract [sv]

    Utveckling av torkschema för industriell luftcirkulationstorkning av furu- och granvirke har generellt medfört en höjning av torkningstemperaturen med fördelar som kortare torkningstid, mindre sprickbildning samt möjlighet att producera virke med minskade deformationer. En följd av att torka virket vid högre temperatur är att virket färgförändras och mörknar samt att kådflytningen ökar. Förutom processparametrar som temperatur, tid och tid i kapillär torkningsfas beror färgförändringar även på virkesegenskaper som extraktivämneshalt och vedens näringsinnehåll. I detta arbete har studier av färgförändring vid värmebehandling av olika virkeskomponenter utförts. Extraktivämnen från extraherad furukärnved och sav (dvs den vätska som finns i splintveden) från furu- och gransplint har värmebehandlats vid 60, 70, 80, 85, 90 och 95°C under 1, 2, 3, 4 och 5 dygn. Med hjälp av en colorimeter, Minolta CR 310, har färgkoordinater i L*, C*, h° rymden uppmätts samt färgskillnaden Delta E*ab före och efter värmebehandling beräknats. För sav har en relativ mätmetod använts där färgmätningar gjorts på filterpapper som indränkts med värmebehandlad sav. Extraktivämnen har värmebehandlats i petriskålar av glas och färgmätning har utförts genom glasskålens botten Resultaten sammanfattas enligt följande: * För ögat klart urskiljbara färgförändringar uppträder hos både sav och extraktivämnen. Ljusheten L* minskar, färgmättnaden C* ökar och färgvinkeln h° går mot mera rött. Färgförändringarna ökar med ökande tid och temperatur * Linjära regressionsmodeller med färgskillnaden Delta E*ab som funktion av tid och temperatur uppvisar höga förklaringsgrader (ca 90%) hos såväl sav som extraktivämnen * Furusav uppvisar signifikant (vid 5% nivå) större färgförändring jämfört med gransav. Skillnaden förklaras troligen av furusavens högre torrhalt vilket är ett mått på kolhydratinnehåll. Endast vinteravverkat virke har ännu undersökts varför variationerna under året och mellan träslagen är en osäkerhet i undersökningen * Hos furusav noteras en accelererad färgförändring vid temperaturer överstigande 70°C * Preliminära försök med värmebehandling av extraktivämnesfri ved i torrt respektive uppfuktat tillstånd visar att värmning i uppfuktat tillstånd orsakar en tydlig ändring av vedens färg. Detta antas bero på att färgade nedbrytningsprodukter bildas vid hydrolys av vedens hemicellulosa

  • 45.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Förfarande vid torkning och bearbetning av brädorPatent (Annet (populærvitenskap, debatt, mm))
  • 46.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    High-temperature drying of Scots pine: A comparison between HT- and LT-drying1995Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, nr 1, s. 95-99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to study the influence of high temperature on wood properties, boards from Scots pine were dried at three different schedules, two high-temperature-schedules (HT) and one at low temperature (LT). Strength properties as hardness, cleavage- and shear-strength were determined and sorption/desorption behaviour were studied. Material was analysed concerning carbohydrate and extractive content and mould growth test at wooden surfaces. Results showed a significant influence of temperature on decreasing shear strength and equilibrium moisture content (EMC) in sorption/desorption tests. Sorption/desorption tests resulted in up to 2.4% lower EMC for HT dried material at the same climate compared with LT-dried and the hysteresis effect seems to be more pronounced in HT-dried material. Mould growth test showed an inhibiting effect of HT-drying on mould susceptibility at wooden surfaces. Carbohydrate analysis revealed a lower content of hemicelluloses in HT-dried boards which indicates a decomposition of the hemicelluloses explaining the decrease in shear strength and hygroskopic moisture uptake seen in the HT dried boards.

  • 47.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Impact of drying and heat treatment on physical properties and durability of solid wood2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    During drying and heat treatment, wood is exposed to a hygrothermal process during which wood properties are chemically and physically affected, resulting in responses on a microscopic as well as on a macroscopic level. The main objective of this thesis is to build knowledge on the interaction between the wood material properties and the drying and heat treatment process in terms of material responses. Hopefully, the benefit of the compiled conclusions in this thesis will contribute to the knowledge base on which decisions are made regarding choice of material and control process parameters in order to attain desired quality in end products. The results are summarized as follows: In this study of material properties such as extractive content and its influence on diffusivity, it is shown that density has greater influence than extractive content on diffusivity in pine and spruce. Pine showed lower diffusivity than spruce, but when extractives were removed from pine heartwood, no difference was found in diffusivity compared to pine sapwood or spruce heartwood. The relation between diffusion coefficients in tangential, radial and axial directions in solid pine sapwood was found to be 1:1.8:7 respectively. Phenomena within the area of process dynamics were also studied. Calculations of thickness of a thin, dry outer shell formed in pine sapwood boards early in the capillary phase of drying were done based on temperature and mass flux measurements. Comparison with dry shell thickness analysed in a computer tomography scanner showed fairly good agreement and was supported by SEM studies of the dark-coloured shell zone in pine sapwood. The following responses to drying and heat treatment process were studied: strength, sorption/desorption behaviour, dimensional stability, colour changes, capillary water absorption capacity and natural durability. A decrease of shear strength along grain direction was found for high-temperature dried pine i.e. at temperatures exceeding 100°C, compared to boards dried at lower temperatures. No unambiguous decrease of surface hardness, cleavage strength or toughness was found at the same temperature comparison. Noticeable colour-change responses to heat treatment were found when different wood constituents such as pine and spruce sap and extractives from pine heartwood were heat-treated separately. Colour changes increased with time and temperature. An accelerated colour change was found for pine sap and extractives at temperatures exceeding 70°C. Computer tomography studies of capillary water absorption in heat-treated and dried pine, spruce and birch showed that heat treatment results in a decreased ability to transport free water in the longitudinal direction in all wood types studied except for pine sapwood. The differences in absorption capacity between spruce sapwood, spruce heartwood and pine heartwood were small. SEM studies of the anatomical microstructure were done with focus on the crossfield pits between horizontal ray parenchyma and longitudinal tracheids in pine and spruce. Crossfield pits in heat-treated and dried pine sapwood were found to be considerably more open than those of not artificially dried sapwood, with partly loose or ruptured membranes. No difference in share of open crossfield pits was found between the material dried at 60°C and material heat-treated at 170°C and 200°C. In pine heartwood, the open, ruptured structures found in heat-treated pine sapwood were rare. A hypothesis involving the emptying of the parenchyma cells has been proposed to explain this observation. The open crossfield structures between ray parenchyma and longitudinal tracheids in dried and heat-treated pine sapwood are believed to play an important role in explaining the differences in water absorption between pine and spruce sapwood. The impact of drying on the natural durability of pine lumber was studied, with mass loss in a rot test as a measure of durability. Air-dried heartwood showed the best durability compared to kiln-dried at 70°C, 90°C and 110°C. Lowest durability was found when drying was performed at 90°C with high material temperature early in the capillary regime of drying with high moisture content. The interpretation is that the duration of high material temperature at high moisture content is a critical state for decay resistance in heartwood. Steam conditioning after drying was found to diminish the durability of sapwood. The relation between mass loss in rot test and concentration of total phenolics-compounds known to contribute to the natural durability of pine heartwood-showed a weak negative correlation, as did the relation between mass loss and density. Heating of extractive-rich green sawdust caused a reduction of phenolics with temperature and time.

  • 48.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Kådved hos furu: Litteraturstudie 19971997Rapport (Annet vitenskapelig)
  • 49.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Mögeltest av torkade furu, gran och contorta bräder: Sammanfattning av “Mould susceptibility of dried boards of Contorta pine, Scots pine and Norway spruce A comparative study” Faksawat Poohphajai, februari 2018. 2018Rapport (Annet vitenskapelig)
    Abstract [sv]

    Resultaten av denna jämförande studie av mögelbenägenhet hos torkade splintvedsrika bräder av furu, gran och contorta sammanfattas enligt följande:

    • Med en kombination av hyvling och behandling med mögelhämmande medel Grön-Fri kan risken för mögelpåväxt avsevärt minskas för samtliga träslag jämfört med ohyvlat/ obehandlat virke.

     

    • Även enbart hyvling eller enbart behandling med Grön-Fri minskar mögelpåväxten jämfört med ohyvlat/obehandlat virke. Det går dock inte i denna studie avgöra om någon av dessa två kombinationer är effektivare än den andra.

     

     

    • För obehandlat/ohyvlat virke uppvisar furu signifikant högre mögelgrad jämfört med gran och contorta.

     

    • Tendensen finns att contortan visar lägst mögelbenägenhet men detta bör betraktas med försiktighet då contortavirket innehöll kärnved. Anledningen till detta var att kärnvedsfria contortabräder ej fanns tillgängliga när studien inleddes.
  • 50.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Properties of solid wood: responses to drying and heat treatment2005Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The hygro-thermal processes that wood is exposed to during drying and heat treatment lead to different reactions or responses in the wood material. The objective of this thesis has been to study the impact of different drying and heat-treatment strategies on various responses, such as strength, sorption/desorption behaviour, dimensional stability and colour changes. A decrease of shear strength along grain direction was found for high- temperature dried pine that was dried at temperatures exceeding 100°C, compared to boards dried at lower temperatures. No unambiguous decrease of surface hardness, cleavage strength or toughness was found for clear wood samples when high-temperature dried material was compared to material dried at lower temperatures. A decrease of hygroscopicity for wood exposed to increased temperatures was found. The higher the temperature, the greater was the decrease in equilibrium moisture content, EMC. The desorption isotherm of dried pine wood compared to initial desorption isotherm for fresh, green wood also showed lower EMC. Noticeable colour-change responses to heat treatment were found when different wood constituents such as pine and spruce sap and extractives from pine heartwood were heat-treated separately. Colour changes increased with time and temperature. An accelerated colour change was found for pine sap and extractives at temperatures exceeding 70°C. Studies of material properties such as extractive content and its influence on diffusivity show that density has greater influence than extractive content on diffusivity in pine and spruce. Pine shoved lower diffusivity than spruce, but when extractives were removed from pine heartwood, no difference was found in diffusivity compared to pine sapwood or spruce heartwood in a comparison of average levels between unpaired groups. The relation between diffusion coefficients in tangential, radial and axial direction in solid pine sapwood were found to be 1:1.8:7 respectively. Phenomena within the area of process dynamics were also studied. Calculations of thickness of a thin, dry outer shell formed in pine sapwood boards early in the capillary phase of drying were done based on temperature and mass flux measurements. Comparison with dry shell thickness analysed in a computer tomography scanner showed fairly good agreement.

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